Electrical system and device



Feb. 11, 1930. G ADAMS 1,746,754

ELECTRICAL SYSTEM AND DEVICE Filed July 8, 1924 AUDIO Alla/0 mm. 4MB min, 4MB

INVENTOR 322?: G. ADAMS A ORNEY Patented Feb. 11, 193i) UNTED STATES PATENT OFFICE GEORGE G. ADAMS, OF BROOKLYN, NEW YORK, ASSIGNOR TO RADIO CORPORATION OF AMERICA, A CORPORATION OF DELAWARE ELECTRICAL SYSTEM AND DEVICE Application filed July 8,

My invention relates to electrical systems and devices. To be more specific my invention relates to radio receiving systems and transformer coupling means for use therein.

Some of the principal objects of my invention are the provision of a radio receiving system in which a larger number of radio frequency amplifying stages may be employed than have heretofore been possible due to the it so-called back coupling between the various radio frequency amplifying stages producing undesired oscillations; and the eliminationof the damping resistance heretofore employed for damping out the undesired oscil l lations.

Another object of my invention is the provision of transformer couplings between the various radio frequency amplification stages which have substantially no stray fields sur- 13 rounding them. This results in the elimination of back coupling between the various stages.

Another object of my invention is the provision of such a transformer, having low 57': manufacturing cost, simplicity of assembly and substantially no stray fields regardless of its angular mounting position.

Other objects and advantageswill be apparent from the following description of the invention taken in conjunction with the accompanying drawing, in which:

Fig. 1 is a schematic diagram of a radio receiving system in which my transformer coupling means are employed.

Fig. 2 is a perspective view of the transformer core member.

Fig. 3 is a side elevation of the transformer.

Fig. 4 is a plan'view of the transformer.

Fig. 5 is a diagrammatic view indicating 10 the manner in which the primary and secondary windings are wound on the core member.

Referring to Fig. 1, my radio receiving system comprises an antenna 1 connected to one terminal of the primary winding of trans former 2, the other terminal being connected to ground G as shown. The secondary winding' of transformer 2 is connected across the grid-filament of a radio frequency amplifying tube 3, a variable condenser 4 being connected across the secondary windings of 1924. Serial No. 724,765.

transformer 2 for suitably tuning the antenna circuits to the incoming signal waves.

The plate-filament circuit of tube 3 comprises the primary winding of transformer 5 and plate battery B, both connected in series. The secondary winding of transformer 5 is connected across the grid-filament of radio frequency amplifying tube 6 in parallel with the variable condenser 7 for suitably tuning the plate-filament circuit of tube 3, the first stage of radio frequency amplification.

The platefilament circuit of tube 6 comprises the primary winding of transformer 8 and the plate battery B both connected in series. The secondary winding of transformer 8 is connected across the grid-filament of the detector tube 9, having the usual grid condenser 10 and grid leak 11 in shunt therewith. A variable condenser 12 may be connected across the terminals of the secondary winding for suitably tuning the plate-filament circuit of tube 6, the second stage of radio frequency amplification.

The plate-filament circuit of the detector tube 9 may be connected to the sound reproduction device 13 through several stages of audio frequency amplification as shown. The filaments of the tubes 3, 6 and 9 may be energized from a common source of power A and the currents in the individual filaments may be independently controlled by rheostats R. I

While I have shown and described my transformer coupling as embodied in a radio receiving system, I wish it distinctly understood that I do not limit myself to such an embodiment but may employ it in various other electrical circuits where the elimination of back coupling is desired.

Although I have shown and described only two stages of radio frequency amplification in my system, I wish it to be understood that I may employ a considerably larger number of such stages, the schematic diagram of my system being for illustrative purposes only.

It now remains to describe the similar transformer coupling means 2, 5 and 8. Referring to Figs. 2, 3, 4 and 5, the core member 15 comprises a tube of suitable insulating material which may be a phenol-condensation product. Two diametrically opposed vertical slots 00 and 3 are cut in the tube for the reception of the primary and secondary windings. Holes 16, 17, 18 and 19 for the reception of terminals are drilled or punched in the circumferential surface of the tube below the bottoms of the slots 00 and y. Holes 16 and 17 for the reception of the primary coil terminals are located to the left of slot 00, while holes 18 and 19 for the reception of the secondary coil terminals are located to the right of slot ac.

The transformer is wound in the following manner special reference being directed to Fig. 5. One extremity of the conductor (represented by a solid line) constituting the primary coils is secured to the binding post 17' and one extremity of the conductor (repreresented by a broken line) constituting the secondary coils is secured to the binding post 18'. The primary conductor is wound around the outside circumference of the tube 15 until the slot 00 is reached, the winding be ing in a counterclockwise direction. The conductor is then passed thru the slot m over to and thru the slot y and then around the outside circumference of the tube 15 in a clockwise direction until opposite the binding post 18 Where the conductor constituting the secondary coils is picked up. Both conductors are then wound together in a clockwise direction until the slot at is reached. They are both passed thru the slot m to and thru the slot g to the left of slot 3 They are then both wound together in a counterclockwise direction around the outside circumference of tube 15 and are then passed thru the slots 00 and y.

Emerging from the slot 3 they are again wound together in a clockwise direction around the outside circumference of the tube 15. After a sufficient number of primary turns have been wound on in the above described manner, the other extremity of the primary conductor is passed thru a hole 20 drilled near the top of the tube 15 and diametrically opposite the terminal 16' and carried down and secured to the terminal 16'.

In a similar manner, the other extremity of the secondary conductor is passed thru the drilled hole 21 diametrically opposite the terminal 19 and is secured thereto. Fig. 5 is of course purelyfor illustrative purposes as only a very limited number of primary and secondary turns are shown. The transformer may be provided with suitable brackets for securing the same to a rapport.

If a current is assumed flowing in the primary winding as shown by the arrows. the lines of magnetic flux due to the left hand turns of the primary winding will tend to be in an upward direction in the outside space to the left of tube 15 and in a downward direction in the space inside tube 1.5-, T lines of magnetic flux due to the right hand turns of the primary winding will tend to be in a downward direction in the outside space to the right of tube 15 and will tend to be in an upward direction in the space inside of the tube. These two fluxes being in opposite directions will neutralize each other resulting in the substantial elimination of external magnetic fields in the outside space around the transformer. The substantial elimination of external magnetic fields due to the secondary coils is similarly effected. The elimination of the external magnetic fields results regardless of the position in which the transformer is mounted.

While I have shown and described my transformer for use in radio receiving systems, I do not limit myself to such use but may design it and use it for other purposes where a transformer coupling possessing similar characteristics is desired.

While I have shown and described preferred embodiments of my invention, I do not limit myself to said embodiments; but may employ such other embodiments as come within the spirit and scope of the invention.

Having described my invention what I claim is:

1. A transformer comprising a cylindrical core member having two diametrically opposed vertical slots and primary and secondary windings wound around the external cylindrical surface of the core member and solely thru the slots-to form a plurality of substantially double D shaped coils successive turns of said primary winding being interlaid between the successive secondary turns.

2. A transformer comprising a hollow cylindrical member provided with a pair of opposed slots, two pairs of terminals carried by said member adjacent one slot, a primary winding comprising a single layer of wire connected to one pair of terminals, and a secondary winding connected to the other pair of terminals, said windings being wound thru said slots and about the cylindrical member to form a pair of substantially double D shaped coils.

3. A transformer comprising a cylindrical member having a pair of opposed slots and a pair of apertures, two pairs of terminals mounted on said member near one end thereof, a primary winding attached to one terminal and strung thru one aperture and thence wound about said member and thru said slots to form a pair of D shaped coils, the free end of the winding being attached to another terminal, and a secondary winding attached to the other pair of terminals, said winding being strung thru the other aperture and wound into coils similar to the primary winding.

4. A radio frequency transformer comprising a cylindrical member provided with a pair of slots, a, primary and a secondary Winding each wound around said member and solely thru said slots and comprising a plurality of turns and said turns being so formed that the stray magnetic field is substantially nil, the successive turns of said primary being spaced apart and the turns of said secondary winding being wound in said spaces between the primary turns, whereby close coupling between primary and secondary is secured and the turn-to-turn capacity of said primary is small.

GEORGE G. ADAMS. 

